Multiple video devices are sometimes used together to produce a video image. One of the video devices can be a graphics computer. But, in linking the video devices, the video devices have to be synchronized to each other. The signal from one has to line up with the signal from the other. A synchronizing device which can reside in one of the video devices is used for the synchronization. The synchronizing device analyzes the reference sync signal from the other video devices. To synchronize vertically, the synchronizing device has to ascertain the beginning of the frame from the video reference signal of the video signal using a frame detector. This video reference signal is also called the composite sync signal and is a train of pulses of different width, as well as different time intervals between pulses. The beginning of frame information is used to synchronize the video signals.
One prior synchronizing device detects the start of a frame by looking for serration pulses after the equalization pulse. However, this prior device is "hard wired" and only accepts a limited number of video formats. When new video formats are developed, the prior synchronizing device is unable to handle the new format. With each new video format, new circuitry and a new synchronizing device has to be developed.
Thus, what is needed is a programmable synchronizing device which can accept a variety of different video formats and which can be programmed to accept a new video format.